Kangaloon Aquifer Issues

Monday, July 24, 2006

Article in the National Parks Association Newsletter

19 July 2006

Due to the continuing drought and declining storages, the Sydney Catchment Authority (SCA) is proposing to tap into groundwater resources in the Southern Highlands, to supply around 15 gigalitres (15 billion litres) of water annually to the Upper Nepean and Avon Dams for up to 3 years, once levels in the dams reach a critical low point of around 40% capacity. As of 13 July 2006, storages were at 41.5%, so there is not a lot of time. This is one of several measures being used to secure Sydney's water supply, and this site is one of 3 prospective sites surrounding Sydney, and is most advanced in terms of monitoring and testing. The borefield would comprise 50-60 production bores with an area impacted of approximately 200 km2.

The aquifer near Kangaloon has generally very high quality water and high yields, with the water table close to the surface (3-20m depth). Groundwater flows from the south to the north. The water would be pumped from between 80-100 m depth and then released (once treated for iron and manganese if present) into the Upper Nepean and Little River. A piped option rather than run-of-river, is also being considered. The technical studies completed to date suggest that a hole would be created in the water-bearing zone, with drawdowns of around 40–80 m close to the bores, with a 10m drawdown approximately 2 km from the borefield, which to the south is close to, but not at Wingecarribee Swamp. Full recovery of the aquifer may take up to 7 years, but is dependent on rainfall events. It has been suggested that flows to creeks and rivers near to the borefield would be impacted but further north where the main discharge areas are in the Nepean River, there would be minimal impact, although the discharge areas, as they are so diffuse, cannot be measured.

Impacts on sensitive areas are being assessed, but are not completed, and it has been shown that Butlers Swamp is a rain-fed swamp and was not affected by the pumping tests, however there could be detrimental impacts on Stockyard Swamp, a sandstone wet swamp. These swamps are listed as being of National significance under Federal law (EPBC Act, 1999). One report states “stream and swamp losses are likely to be in the order of 18-36 percent of the total volumes pumped from groundwater after two years”. The SCA managed "Special Areas" are to the north of the proposed borefield, and yet it is this high conservation value land that will be most impacted by the proposal.

Sydney uses around 1.5 gigalitres per day, so this additional supply won’t address the long term unsustainable water supply system, however the impacts on our local streams and rivers could be very detrimental, and cause a "drying up" of the landscape. Residents are experiencing Level 3 restrictions, which are not very onerous. More savings can be made with further demand management, especially as around 28% of those residents recently surveyed felt that the restrictions were not severe enough (60% of respondents thought that they were "about right"). While attitudes to water have improved dramatically during this drought, only a tiny number of residents have taken up the tank rebate and installed a rainwater tank. More tanks would reduce the pressure on the catchments and groundwater surrounding Sydney. More positively, around 330,000 households have installed water efficient devices, through Sydney Water’s retro-fit program. BASIX is helping to mitigate some of the growth in demand in new housing estates, however with new releases of around 40000 homes in Western Sydney, and with the current rate of water usage, the water from this aquifer would barely meet the demand of these new homes.

The groundwater in the Southern Highlands has not been managed very well in the past, however no more high yield bores (for commercial purposes) can be constructed due to embargoes enacted in 2004 and 2005, for a total of 12 parishes in a large area around Mittagong, Bowral, Sutton Forest and Burrawang. Incremental demand has occurred through basic right provisions for stock and domestic purposes, which are given a high level of protection, but unfortunately this provision has been misused by landholders who sink bores for ornamental lakes, other water features and extensive European gardens.

A "win-win" approach, following all these investigations would be to protect and conserve the groundwater resource for future generations and the environment, or for emergency drinking water supply only.

As a member of the recently formed Upper Nepean Groundwater Community Reference Group (CRG), for the proposed borefield at Kangaloon (near Robertson), I am helping to critique the proposal, advise the government, and communicate with the public. If you would like to know more, or have a say, visit the blog shown below, or the SCA website www.sca.nsw.gov.au.


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